1. Field of the Invention
The present invention relates to an ATM exchange used in an ATM communications system, and more particularly to an ATM exchange capable of performing camp-on registration.
2. Description of the Related Art
An ATM (Asynchronous Transfer Mode) communications system comprises a network in which a plurality of ATM exchanges are connected by transmission lines, and terminals connected to each ATM exchange.
In a common ATM communications system, a terminal notifies an ATM exchange of the desired band, quality, and other connection requirements when a call connection is requested. The ATM exchange investigates whether or not sources that satisfy these connection requirements can be found, performs the call connection when this can be offered, and notifies this terminal that the connection is denied when this cannot be offered. A terminal whose call request has been accepted performs communication, whereas a terminal that has been notified of a connection refusal repeats its requests for a call connection until it is accepted.
There are also ATM communications systems that use ATM exchanges capable of camp-on request registration. In such ATM communications systems, a terminal that has been notified of a connection refusal can issue a camp-on request, and the ATM exchange that has received the camp-on request monitors an empty band value and grants permission to communicate to the terminal that has issued the camp-on registration when the empty band value exceeds the band value required for the camp-on request.
The structure and operation of a conventional ATM exchange capable of performing camp-on registration will now be described in further detail with reference to FIG. 50.
As shown in the figure, a conventional ATM exchange 100 comprises a subscriber""s line circuit 30, a switching unit 20, an output buffer 40, a control device 200, and a storage device 300 as its main constituent elements. The subscriber""s line circuit 30 is a circuit for providing an interface with terminals T1 through Tn; the switching unit 20 identifies the addresses from the headers of the cells (fixed-length data that constitute a portion of the communications content) that have been inputted via the subscriber""s line circuit 30, and presents the address to the output buffer 40. The output buffer 40 temporarily accumulates the cells and sends them out over a transmission line 50.
The control device 200 monitors the operating condition (empty band value #0) of the transmission line 50 and changes the empty band value #0 in accordance with the used or released band value when a call connection or disconnection occurs. The empty band value #0 and the required band value are compared with each other and connection receipt management is performed when a call connection has been requested. For example, the requested call is connected and the empty band value #0 is reduced by #Ti when a call connection requiring a band value #Ti ( less than #0) has been made from a terminal Ti. Meanwhile, a terminal Tj is notified of a refusal to connect when a call connection requiring a band value #Tj ( greater than #0) has been made from the terminal Tj.
In addition, when a camp-on request have been issued from a terminal, the control device 200 registers the content thereof in the storage device 300. Every time a band value is released due to disrupted communication, it is determined whether or not the empty band value #0 exceeds the band value required for the registered camp-on request, and a call that corresponds to this camp-on request is established on the transmission line 50 when the empty band value #0 has exceeded the required band value.
As described above, in a conventional ATM exchange it is determined whether or not a connection request has been received based on the empty band value #0. The determination as to whether or not permission has been granted with respect to a camp-on request is also performed based on the empty band value #0. In a conventional ATM exchange, therefore, when a request is received for a call connection that uses a band below the empty band value after a camp-on request has been registered, a long time is often needed to finally establish a call in accordance with this connection request. For example, a long time is often needed before a camp-on request that requires a substantial band value is executed, as when television images are transmitted.
An object of the present invention is to provide an ATM exchange in which a permission for a camp-on request is issued in a short time.
The first ATM exchange pertaining to the present invention receives from terminals call connection requests and camp-on requests in which the band values being used are specified, and establishes on a transmission line calls for which the specified band values can be used, wherein this ATM exchange comprises a band value storage unit, a camp-on request storage unit, a connection request response unit, a camp-on request registration unit, a band value setting unit, a band value updating unit, a camp-on request response unit, and a post-processing unit.
The band value storage unit divides the unused band value of the transmission line into a empty band value and temporarily saved band value, and stores them. The camp-on request storage unit stores the contents of camp-on requests issued by each terminal, in correlation with the processing rank of these contents.
The connection request response unit establishes on the transmission line the call requested by a connection request when the connection request received from a terminal is one for which the use of a band value below the empty band value stored in the band value storage unit has been specified, and notifies the terminal of a refusal to connect when the connection request is such that the use of a band value exceeding the empty band value has been specified. In addition, the camp-on request registration unit, upon receipt of a camp-on request from a terminal, establishes the processing rank of this camp-on request and performs registration in the camp-on request storage unit in correlation with the processing rank that identifies the camp-on request data that represent the contents of this camp-on request. The band value setting unit adds the empty band value stored in the band value storage unit to the temporarily saved band values stored in the band value storage unit, and setting zero for the empty band value in the band value storage unit, when the registration of camp-on request data by the camp-on request registration unit is performed with respect to a camp-on request storage unit in which no camp-on request data have been registered.
The band value updating unit adds a band value released by a disconnected call to a temporarily saved band value stored in the band value storage unit when camp-on request data have been registered in the camp-on request storage unit upon detection of the disconnected call in the transmission line. In addition, the band value updating unit adds a band value released by a disconnected call to an empty band value stored in the band value storage unit when no camp-on request data have been registered in the camp-on request storage unit upon detection of a disconnected call in the transmission line.
The camp-on request response unit establishes a call that corresponds to camp-on request data in the transmission line when the temporarily saved band value stored in the band value storage unit exceeds the band value specified for use by the camp-on request data that are stored in the camp-on request storage unit and that are assigned the highest processing rank. The post-processing unit reduces the temporarily saved band value stored in the band value storage unit by the band value used to set up a call when it is set up by the camp-on request response unit, and erases the camp-on request data that is stored in the camp-on request storage unit and that have been used by the camp-on request response unit.
Specifically, in the first ATM exchange of the present invention, band value not used for communication are monitored and divided into the empty band value used to determine whether or not a connection request has been received, and the temporarily saved band value used to determine whether or not there has been a response to a camp-on request, and the band values that have been released following receipt of a camp-on request are all used for camp-on requests. A terminal connected to the first ATM exchange can therefore start communication soon after a camp-on request has been issued.
The camp-on request registration unit adopted for use in the first ATM exchange of the present invention may be a unit for assigning to camp-on request data a processing rank indicating that a processing sequence is to be conducted following the processing of the camp-on request data registered in the camp-on request data storage unit when the camp-on request data are registered for a newly received camp-on request.
In addition, a second ATM exchange can be obtained by further providing the first ATM exchange with a class storage unit for storing classes assigned to different terminals. The addition of a class storage unit, however, leads to the use of a camp-on request registration unit for changing the processing rank of each piece of the camp-on request data in the camp-on request storage unit in such a way that the camp-on request data are processed in accordance with a sequence that corresponds to the classes assigned to terminals and stored in the class storage unit when camp-on request data concerning camp-on requests newly received from the terminals are registered in the camp-on request storage unit.
Setting up a communications system in which a second ATM exchange thus configured is used allows camp-on requests to be processed in accordance with the priority ranks that correspond to the classes of terminals, making it possible to conduct effective communication.
It is also possible to further provide the first ATM exchange of the present invention with a time-specific class storage unit for storing classes related to different terminals for each time period, and to adopt as a camp-on request registration unit a unit for changing the processing rank of each piece of the camp-on request data in the camp-on request storage unit in such a way that the camp-on request data are processed in accordance with a sequence that corresponds to the classes assigned to terminals at the present moment and stored in the class storage unit when camp-on request data concerning camp-on requests newly received from the terminals are registered in the camp-on request storage unit.
The second ATM exchange of the present invention can be further provided with a second class storage unit for storing a second type of class data and waiting time data concerning each terminal; a selection unit for selecting, from among the camp-on request data stored in the camp-on request storage unit, camp-on request data in which the time that has elapsed following registration exceeds the waiting time data stored in the second class storage unit for a terminal that has issued a camp-on request; and a second processing rank change unit for changing the processing rank of each peace of the camp-on request data stored in the camp-on request storage unit in such a way that the camp-on request data selected by the selection unit are processed in accordance with an order that corresponds to the second class stored in the second class storage unit for the terminal that has issued this camp-on request.
An allocated band value storage unit for storing interrelations between terminals and allocated band values can also be added to the first ATM exchange of the present invention. The connection request response unit used in this case may be a unit for issuing a refusal to connect when a band value is higher than the allocated band value stored in the allocated band value storage unit for a terminal, even in cases in which a connection request that requires the use of a band value below the empty band value in the band value storage unit has been received from the terminal. In addition, the camp-on request registration unit used may be a unit for issuing a refusal to register a camp-on request from a terminal when the band value specified for use with the camp-on request received from the terminal is higher than the allocated band value stored in the allocated band value storage unit for this terminal.
The second ATM exchange of the present invention can be further provided with a class-specific allocated band value storage unit fir storing interrelations between classes and allocated band values. The connection request response unit used in this case may be a unit for issuing a refusal to connect when a band value is higher than the allocated band value stored in the class-specific allocated band value storage unit for the class of a terminal, even in cases in which a connection request that requires the use of a band value below the empty band value in the band value storage unit has been received from the terminal. In addition, the camp-on request registration unit used may be a unit for issuing a refusal to register a camp-on request from a terminal when the band value specified for use with the camp-on request received from the terminal is higher than the allocated band value stored in the class-specific allocated band value storage unit for this terminal.
A secured empty band value storage unit for storing interrelations between terminals and secured empty band values can also be added to the first ATM exchange of the present invention. The connection request response unit used in this case may be a unit for establishing a requested call on the transmission line only in those cases in which the value stored in the band value storage unit when a call connection has been requested by a terminal is the empty band value that exceed the value obtained by adding the requested band value and the secured empty band value stored in the secured empty band value unit for this terminal. In addition, the camp-on request registration unit used is a unit for adding the secured empty band value stored in the secured empty band value unit for the terminal that has issued a camp-on request to the temporarily saved band value in the band value storage unit, and for subtracting this secured empty band value from the empty band value in the band value storage unit, when a camp-on request has been received in the absence of an object of monitoring (camp-on request).
A class-specific secured empty band value storage unit for storing interrelations between classes and secured empty band values can also be added to the second ATM exchange of the present invention. The connection request response unit used in this case may be a unit for establishing the requested call on a transmission line only in those cases in which the value stored in the band value storage unit when a call connection has been requested by a terminal is the empty band values that exceed the values obtained by adding the requested band value and the secured empty band value stored in the class-specific secured empty band value unit for this terminal. In addition, the camp-on request registration unit used is a unit for adding the secured empty band value stored in the class-specific secured empty band value unit for the terminal that has issued a camp-on request to the temporarily saved band value in the band value storage unit, and for subtracting this secured empty band value from the empty band value in the band value storage unit, when a camp-on request is received in the absence of a monitoring object.
A caller-specific class storage unit for storing the interrelations between classes and caller identification information can also be added to the first ATM exchange of the present invention. The unit used as the camp-on request registration unit in this case is a unit for changing the processing rank of each peace of the camp-on request data in the camp-on request storage unit in such a way that the received camp-on request is processed in accordance with a sequence that corresponds to the class stored in the caller-specific class storage unit in correlation with the identification information contained in this camp-on request.
In addition, the unit used as the connection request response unit should be a unit for providing information about the number of pieces of the camp-on request data registered in the camp-on request storage unit when a terminal has been given a message that a connection has been refused.
A third ATM exchange of the present invention receives terminal-originated requests for call connections for which the band value to be used are specified, and establishes a call in which the specified band value can be utilized in a transmission line, wherein this ATM exchange comprises a band value storage unit, a camp-on request storage unit, a connection request processing unit, a band value setting unit, a band value updating unit, a camp-on request response unit, and a post-processing unit.
The band value storage unit is used to divide the unused band value of a transmission line into an empty band value and a temporarily saved band values, and to store them. The camp-on request storage unit is used to store the contents of camp-on requests in correlation with the processing ranks thereof.
The connection request processing unit establishes on a transmission line a call requested by a connection request when the connection request received from a terminal is one for which the use of a band value below the empty band value stored in the band value storage unit has been specified. In addition, the connection request processing unit considers a connection request to be a camp-on request when the processing rank received from a terminal is one for which the use of a band value above the empty band value stored in the band value storage unit has been specified, establishes the processing rank of this camp-on request, and performs registration in the camp-on request storage unit in correlation with the processing rank that identifies the camp-on request data that represent the contents of this camp-on request.
The band value setting unit adds the empty band value stored in the band value storage unit to the temporarily saved band value stored in the band value storage unit, and setting zero for the empty band values in the band value storage unit, when the registration of camp-on request data by the camp-on request processing unit is performed with respect to a camp-on request storage unit in which no camp-on request data have been registered.
The band value updating unit adds a band value released by a disconnected call to a temporarily saved band value stored in the band value storage unit when camp-on request data have been registered in the camp-on request storage unit upon detection of a disconnected call in the transmission-line. In addition, the band value updating unit adds a band value released by a disconnected call to an empty band value stored in the band value storage unit when no camp-on request data have been registered in the camp-on request storage unit upon detection of a disconnected call in the transmission line.
The camp-on request response unit establishes a call that corresponds to camp-on request data-in the transmission line when the temporarily saved band value stored in the band value storage unit exceeds the band value specified for use by the camp-on request data that are stored in the camp-on request storage unit and that are assigned the highest processing rank. The post-processing unit reduces the temporarily saved band value stored in the band value storage unit by the band value used to set up a call when it is set up by the camp-on request response unit, and erases the camp-on request data that is stored in the camp-on request storage unit and that have been used by the camp-on request response unit.
Specifically, when a connection request cannot be received, the third ATM exchange considers this connection request to be a camp-on request and registers it.